The present invention generally relates to ultrasonic ranging and, more particularly, to an ultrasonic ranging system and method for improving the accuracy of an ultrasonic transducer, especially for use in a vehicle.
Ultrasonic sensing techniques have become widely acceptable for use in ranging systems for determining the presence of and distance to a target object. In a conventional ultrasonic ranging system, an ultrasonic transducer is employed which converts electrical signal pulses into mechanical motion. In turn, the mechanical motion creates ultrasonic sound waves that are transmitted through the atmosphere in a desired direction. Provided there is a target in its path, the ultrasonic sound waves reflect off of the target and the reflected sound waves travel back to the ultrasonic transducer. The reflected sound waves, also referred to as the echo waves, mechanically deflect the ultrasonic transducer and, in response, a low voltage signal is generated. Since the speed of travel of the sound waves remains relatively fixed, the distance to the target is determined by measuring the time period between the transmitted and received signal pulses, and computing the distance as a function of the time period and the sound wave speed.
In the past, conventional ultrasonic ranging systems employed a series of gated signal pulses of uniform amplitude to drive the ultrasonic transducer. In order to compute the distance to a target, the conventional ultrasonic ranging system measured the time period between the beginning of the transmitted drive signal and the beginning of the received echo signal. The time period measurement between the transmitted and received signals was typically multiplied by one-half the speed of travel of the sound waves to compute the measured distance to the target. The conventional distance measurement approach has drawbacks in that the accuracy of the ultrasonic distance sensing system can be influenced to a large extent by several factors such as the geometry and the material of the target object, as well as variations in the transmit signal. Accordingly, conventional ultrasonic ranging systems are capable of providing inaccurate distance measurement.
Accordingly, it is one object of the present invention to provide for a method of effectively enhancing the accuracy of distance measurement with an ultrasonic ranging system. It is another object of the present invention to provide for an ultrasonic ranging system with enhanced accuracy for determining distance to a target. Yet, it is a further object of the present invention to provide for an enhanced accuracy ultrasonic ranging system for use in the passenger compartment of a vehicle.